Lecture 1-2 - Welcome ENGR 225. Thermodynamics, Fluid...

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Unformatted text preview: Welcome ENGR 225. Thermodynamics, Fluid Dynamics, Heat and Mass Transfer David H. Matthiesen, Ph.D. Associate Professor, Primary Appt., Department of Materials Science and Engineering Secondary Appt., Department of Mechanical and Aerospace Engineering Director, Wind Energy Research and Commercialization (WERC) Center Director, Wind Energy Section, Great Lakes Energy institute ENGR 225. Thermodynamics, Fluid Dynamics, Heat and Mass Transfer (4) Elementary thermodynamic concepts: first and second laws, and equilibrium. Basic fluid dynamics, heat transfer, and mass transfer: microscopic and macroscopic perspectives. Prereq: CHEM 111, ENGR 145, and PHYS 121. Coreq: MATH 223. A quad is a million billion BTUs Course Goals Florence, 14th Century painting Florence, 16th Century Painting Knowledge is a human-made artifact. When your views of reality are changed by knowledge, Reality itself changes. That is the day the universe changed for you. epistemology – metaphysical subjectivism – cogito ergo sum Issac Newton 1687 Philosophiæ Naturalis Principia Mathematica, Latin for "Mathematical Principles of Natural Philosophy“ Second law: The acceleration a of a body is parallel and directly proportional to the net force F and inversely proportional to the mass m, i.e., F = ma Two materials with the same mass, according to Newton, 1. have the same potential energy (PE = mgh) (statics) and 2. have the same kinetic energy (KE = 1/2mv2) (dynamics) Issac Newton 1687 Philosophiæ Naturalis Principia Mathematica, Latin for "Mathematical Principles of Natural Philosophy“ Second law: The acceleration a of a body is parallel and directly proportional to the net force F and inversely proportional to the mass m, i.e., F = ma Gedankenexperiment Now heat these materials to the same temperature and place them on a block of paraffin wax (mp = 37oC) What you will find is that, after some time, the two materials will ‘sink ‘ to different depths Why? Because the movement (dynamics) of heat (thermo) is different in these two materials Even though they have the same mass! Thermodynamics then is the science that Newton missed! i.e. Internal Energy The ‘Laws’ of Thermodynamics 0. There is a thing called temperature 1. The best you can get out is what you put in 2. You can’t even do that 3. Things get more messed up every day Let’s talk about TEMPERATURE Rely on the thermal expansion of liquids 1. Have a reservoir of liquid 2. Have a small diameter tube for the liquid to rise But if the tube is open – pressure comes into play i.e. it is a barometer too The solution is to seal the top of the tube But what liquid should you use? 1. Newton 1700 used linseed oil coined the name thermo-meter 2. Romer 1701 used pure water 3. Reaumer 1730 used dilute alcohol 4. Daniel Gabriel Fahrenheit 1724 mercury Daniel Gabriel Fahrenheit 1724 How do you calibrate your thermo-meter 1. 2. 3. 4. 0 = water, ice and ammonium chloride 32 = water and ice 96 = blood heat (i.e. body temperature) 64 scale divisions = 26 Anders Celsius 1742 How do you calibrate your thermo-meter 1. 2. 3. 4. 5. 6. 7. 0 = boiling point of water -100 = freezing point of water Carolus Linnaeus - 1744 Reversed scale For over 200 years know as centigrade (oC) Confused with centisimal (1/10,000 of right angle) 1948 SI convention oC = degrees Celsius Sir William Thomson Lived in the river Kelvin in the town of Largs on the Firth of Clyde in North Ayrshire just outside Glasgow, Scotland 1. Why was he knighted? 2. 1st Baron Kelvin of Largs 1848 “a unit of heat descending from a body A at a temperature T of this scale, to a body B at a temperature (T-1) would give out the same mechanical effect [work], whatever be the number T” Absolute zero = the point at which no further heat could be transferred K = oC +273 William John Macquorn Rankine wrote in 1853: Definition of equal temperatures. Two portions of matter are said to have equal temperatures, when neither tends to communicate heat to the other. 1859 Defines absolute temperature scale in terms of oF R = oF +460 James Clerk Maxwell 1872 If when two bodies are placed in thermal communication, one of the two bodies loses heat, and the other gains heat, that body which gives out heat is said to have a higher temperature than that which receives heat from it. If when two bodies are placed in thermal communication neither of them loses or gains heat, the two bodies are said to have equal temperatures or the same temperature. The two bodies are then said to be in thermal equilibrium. Bodies whose temperatures are equal to that of the same body have themselves equal temperatures Peter Guthrie Tait 1894 if A is at the same temperature as B and also at the same temperature as C — no transfer of heat takes place between B and C, whatever be these bodies the zeroth law of thermodynamics If two assemblies are each in thermal equilibrium with a third assembly, they are in thermal equilibrium with each other ...
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